Current therapies are limited to small molecules because cells are impervious to large molecules such as proteins. We developed a method to transport proteins into cells as molecular fusion proteins including a fragment or portion of a mAb 3E10, a cell-penetrating antibody. mAb 3E10 is unique and distinguishable from other cell-penetrating peptides (CPPs) or protein transduction domains (PTDs) by its use of hENT2 nucleoside salvage pathway for entry into cells. We also developed single chain variable fragments of 3E10 antibody (3E10 scFv), including conservative variants thereof joined to e.g. heat shock proteins and glucose regulated proteins (e.g., GRP78 (glucose-regulated-protein 78 kDa). The full 3E10 antibody has been previously described (Weisbart R H, et al. J Immunol. 1990 144(7): 2653-2658; ATCC Accession No. PTA 2439 hybridoma). Our results demonstrate the feasibility of transporting proteins and other large molecules into cells using the fusion proteins of the invention.